Mechanisms of brain injury in infantile child abuse

Prevalence, Patterns, and Clinical Relevance of Hypoxic-Ischemic Injuries in Children Exposed to Abusive Head Trauma

BACKGROUND AND PURPOSE

Hypoxic-ischemic injuries (HIIs) are a scarcely investigated but important cause of morbidity and mortality in children who suffered abusive head trauma (AHT). The purpose of this study is to determine: (a) prevalence, types, and clinical relevance of cytotoxic edema compatible with HII in nonpenetrating AHT, (b) their relationship to other classic neuroimaging findings of AHT, and (c) their correlation with clinical outcomes.

METHODS

Diffusion-weighted imaging sequences of magnetic resonance imagings performed on children under 5 years diagnosed with AHT were reviewed to detect the most common patterns of acute parenchymal damage. Patterns of cytotoxic edema were described, and HII-compatible ones divided in subtypes. Correlation between HII, fractures, and subdural hemorrhages (SDHs) and with clinical outcomes was determined using imaging and available follow-up data.

RESULTS

Out of 57 patients, 36.8% showed lesions compatible with HII. A predominantly asymmetric cortical distribution was observed in 66.7% of cases, while 33.3% had diffused both cortical and deep gray/white matter distribution injury. Traumatic axonal injuries and focal contusions were less common. There was no significant correlation between the presence of SDH (P = .6) or skull fractures (P = .53) and HII. HII was the most severe form of parenchymal damage in terms of in-hospital mortality and morbidity at follow-up.

CONCLUSIONS

HII is the most common type of parenchymal damage in children victim of AHT, being present in 1/3 of patients with this condition, and correlates with more severe outcomes. Its presence is independent from other classic traumatic findings such as SDH and fractures.

Imaging of spinal injury in abusive head trauma: a retrospective study

BACKGROUND

Spinal imaging has been a neglected part of abusive head trauma (AHT) imaging. As most of the radiographs and CT spine are negative in AHT in infants, the cervical spine is assumed to be normal. There is increasing evidence in the role of injury to brainstem and cervical cord in the pathogenesis of AHT. In addition, in courts of law, there is fierce debate about AHT, its mimics and other disparate nontraumatic diagnoses explaining the neuroradiological and skeletal findings. However, this discussion ignores the evidence and significance of spinal injury. We sought to study the cervical spine in an AHT cohort to understand the true prevalence of spinal injuries in AHT and contrast it with cohorts of accidental and nontraumatic groups to give the clinicians a robust diagnostic tool in evaluating AHT.

OBJECTIVE

The purpose of this study is to compare the relative incidence of spinal ligamentous and soft-tissue abnormalities on spinal MRI among three groups of children ages <48 months: 1) those with AHT, 2) those with accidental trauma, and 3) those with nontraumatic conditions.

MATERIALS AND METHODS

This comparative study included 183 children who underwent spine MRI: 67 with AHT, 46 with accidental trauma and a clinical suspicion of spinal injury, and 70 with nontraumatic conditions. Clinical and radiographic findings were collected in all cases and were analyzed retrospectively to identify MRI evidence of traumatic spinal injuries. The incidence of spinal injuries among the three groups was compared. The incidence of spinal ligamentous injuries was calculated for those with and without radiographic evidence of hypoxic-ischemic encephalopathy. All comparisons were performed using Fisher exact test with P < 0.05 considered statistically significant.

RESULTS

Cervical spine ligamentous injuries (predominantly the nuchal, atlanto-occipital and atlanto-axial ligaments) were present in 78% of the AHT group, 46% of the accidental trauma group and 1% of the nontraumatic group; all of these differences were statistically significant. Among the AHT group, ligamentous injuries were statistically correlated with evidence of brain ischemia.

CONCLUSION

Injury to the cervical spinal posterior ligamentous complex is common in AHT and even more prevalent than in clinically symptomatic traumatic cases. The high correlation between the radiographic findings of occipitocervical ligamentous injuries and hypoxic-ischemic brain injury is consistent with an interpretation that transient upper occipitocervical spinal cord injury in AHT leads to disordered breathing and results in hypoxic-ischemic encephalopathy. We recommend imaging the entire spine in AHT to properly identify and classify these injuries.

The neuropathology of infant subdural haemorrhage

Subdural haemorrhage (SDH) in the infant has a different pattern from that seen in the older child and adult. It is usually a widespread, bilateral, thin film, unlike the thick, space-occupying and often unilateral clot seen in older children and adults after trauma. Whether both arise by the same mechanism is unknown, but it seems unlikely. Most SDH is said to be due to trauma but in infants there are other, atraumatic causes. Birth is also important; recent MRI studies show an incidence of almost 50% in asymptomatic neonates. Traumatic SDH is said to result from rupture of bridging veins but new insights into the anatomy of infant dura suggest a dural origin for thin film subdural bleeding in young babies. Acute SDH usually rapidly resolves, but sometimes develops into a chronic fluid collection. Healing of SDH is by formation of a granulating membrane which may confer vulnerability to rebleeding, either spontaneously or after an otherwise innocuous event. SDH has a particular significance as one of the features of the triad (together with retinal haemorrhage and encephalopathy) associated with non-accidental injury. As the possibility of non-accidental injury is often first raised by a radiologic report of subdural bleeding, it becomes critically important in the interpretation of the scan appearances to understand the unique physiology and anatomy of the infant dura.

Shaken baby syndrome: re-examination of diffuse axonal injury as cause of death

The discussion surrounding shaken baby syndrome (SBS) arose from the lack of evidence implicating diffuse axonal injury (DAI) as a cause of death. It was assumed instead that injury to the cervical cord, medulla, and nerve roots played a causal role. The present pathomorphological study examines 18 selected infants (<1-year-old) whose deaths were highly suspicious for SBS, exhibiting the classical SBS triad of acute subdural hemorrhage (SDH), retinal bleeding, and encephalopathy. Gross autopsy and microscopic findings of these infants were compared with those of 19 victims of sudden infant death syndrome (SIDS; control group 1) and of 14 infants who died of disease or injuries/violence not involving the head, neck or eyes (control group 2). Symptoms of mechanical impact to the head were evident in seven of the SBS infants, but in none of the control infants. DAI was not detected in either the SBS or control cases. Localized axonal injury (AI) was regularly present in the brains of the SBS infants surviving longer than 1.5-3.0 h, but only occasionally in the craniocervical junction and within the nerve roots of the upper cervical cord; it was never present in the medulla. Epidural hemorrhage of the cervical cord was seen in four of the ten examined SBS cases, but in none of the control cases. Based on the absence of DAI in the brain and of signs of generalized cervical cord or nerve root injuries, we conclude that the cause of death in the SBS victims was a global cerebral ischemia secondary to SDH, focal vasospasm, trauma-induced transitory respiratory and/or circulatory failure.

Unilateral hypoxic-ischemic injury in young children from abusive head trauma, lacking craniocervical vascular dissection or cord injury

BACKGROUND

Abusive head trauma (AHT) in young children usually has a severe outcome when associated with hypoxic-ischemic encephalopathy (HIE), which is best characterized by MRI in the acute or subacute phase utilizing diffusion-weighted imaging (DWI). HIE in this setting has been hypothesized to result from stretching of the spinal cord, brainstem, or vasculature.

OBJECTIVE

To provide clinical correlation in patients with unilateral HIE and to postulate a mechanism in the setting of suspected AHT.

MATERIALS AND METHODS

IRB approval was obtained. Over a 5-year period, the medical records and images were reviewed of the 53 children < or = 3 years of age who presented with acute head trauma according to the hospital registry. The children were subselected in order to determine how many suffered either HIE or AHT, and to detect those with unilateral HIE.

RESULTS

In 11 of the 53 children, the etiology of the head trauma was highly suspicious for abuse. In 38 the head trauma was accidental and in 4 the trauma was of unknown etiology and at the time of this report was unresolved legally. Of the 53, 4 suffered HIE confirmed by CT or MRI. In three of these four with HIE the trauma was considered highly suspicious for AHT. Two of these three were the only patients with unilateral HIE, and both (7 months and 14 months of age) presented with early subacute phase HIE seen on DW MRI (range 4-7 days) and are described in detail with clinical correlation. The third child with AHT and HIE had bilateral findings. In the fourth patient the HIE was bilateral and was considered accidental. The work-up for both patients with unilateral HIE included head CT, craniocervical MRI, and craniocervical MR angiography (MRA). In both, there was mostly unilateral, deep white matter restricted diffusion, with subdural hematomas that were small compared to the extent of hypoxic-ischemic insult, and no skull fracture. Craniocervical MRA and axial thin-section fat-saturation images were negative for dissection, brainstem, or cord injury. Legal authorities obtained a confession of inflicted injury in one and a partial confession in the second (which did not fit the extent of injury). Five other children with HIE (based on DWI) were found during this period who had not suffered head trauma; all were bilateral insults.

CONCLUSION

HIE associated with AHT might present with largely unilateral white matter injury on DWI following extensive cortical infarction. We propose that unilateral HIE in a young child might be a sign of AHT and might result from cervical vascular compression, whether from kinking during hyperflexion/hyperextension or from direct strangulation.

Hypoxic-Ischemic Injury Complicates Inflicted and Accidental Traumatic Brain Injury in Young Children: The Role of Diffusion-Weighted Imaging

We evaluated the relationship between clinical features and hypoxic-ischemic injury (HII) shown by diffusion-weighted MRI (DWI) in young children with head trauma, comparing inflicted trauma (IT) to accidental trauma (AT). This single-center consecutive cohort study included children age birth to 36 months admitted for head injury July 2001 to December 2004 with brain magnetic resonance imaging (MRI) obtained < or =1 week, identified from prospectively maintained registries of children with trauma. Clinical and radiological data during the hospital stay were extracted from medical records. MRIs were analyzed by study examiners blinded to clinical status and scored by type, severity and location of lesions attributable to traumatic, hypoxic-ischemic, or mixed injury patterns. 30 IT patients and 22 AT patients met inclusion criteria. IT cases were younger than AT, 3.0 versus 8.5 months. Mean time to MRI in IT (2.1 days) was similar to AT (1.9 days). HII was more common in IT (11 of 30) than AT (2/22, p = 0.03). Children with HII more commonly had seizures, needed intubation at presentation, and needed neurosurgical intervention compared to those without HII. Most patients with HII (10/14) required in-patient rehabilitation compared to those without HII (4/38). Our study is the first to characterize HII using diffusion-weighted MRI in young children, comparing IT and AT. The higher rate of HII on DWI-MRI in IT than in AT is likely multifactorial, involving respiratory insufficiency, seizures, and intracranial mass-occupying lesions requiring neurosurgical intervention. HII predicted need for in-patient rehabilitation in a large majority of children.

A Biomechanical Analysis of the Causes of Traumatic Brain Injury in Infants and Children

There is significant disagreement among medical professionals regarding the mechanisms for infant brain injury. This disagreement is due in part to the failure by some to acknowledge and incorporate known biomechanical data and models into hypotheses regarding causes. A proper biomechanical understanding of the mechanisms of traumatic brain injury (TBI) challenges many published and testified assumptions regarding TBI in infants and children. This paper analyzes the biomechanical relationship between the causes of TBI in infants and children, and their physiological consequences. Loading characteristics, injury parameters and criteria, scaling, failure characteristics, differences between infants and adults, and impact due to falls are described and discussed in the context of the laws of mechanics. Recent studies are critiqued with reference to their contribution to an understanding of brain injury mechanisms. Finally, methods for improving our currently incomplete knowledge of infant head injuries, and their mechanisms, consequences and tolerances are proposed. There is an urgent need for close collaboration between physicians and biomechanicians to objectively and scientifically evaluate infant head injuries to further define their mechanical bases, and to assist in their diagnosis and treatment.

Apnoea and brain swelling in non-accidental head injury

AIMS

(1) To identify whether infants and young children admitted to hospital with subdural haematomas (SDH) secondary to non-accidental head injury (NAHI), suffer from apnoea leading to radiological evidence of hypoxic ischaemic brain damage, and whether this is related to a poor prognosis; and (2) to determine what degree of trauma is associated with NAHI.

METHODS

Retrospective case series (1992-98) with case control analysis of 65 children under 2 years old, with an SDH secondary to NAHI. Outcome measures were presenting symptoms, associated injuries and apnoea at presentation, brain swelling or hypoxic ischaemic changes on neuroimaging, and clinical outcome (KOSCHI).

RESULTS

Twenty two children had a history of apnoea at presentation to hospital. Apnoea was significantly associated with hypoxic ischaemic brain damage. Severe symptoms at presentation, apnoea, and diffuse brain swelling/hypoxic ischaemic damage were significantly associated with a poor prognosis. Eighty five per cent of cases had associated injuries consistent with a diagnosis of non-accidental injury.

CONCLUSIONS

Coma at presentation, apnoea, and diffuse brain swelling or hypoxic ischaemia all predict a poor outcome in an infant who has suffered from SDH after NAHI. There is evidence of associated violence in the majority of infants with NAHI. At this point in time we do not know the minimum forces necessary to cause NAHI. It is clear however that it is never acceptable to shake a baby.

Ethical issues in imaging nonaccidental injury: child abuse

One of the most controversial areas of nonaccidental injury is the medical diagnosis of inflicted central nervous system injury and its impact on medical, social, and legal outcomes for children and families. This review addresses the role of the neuroradiologist in the clinical care of the pediatric patient and as an expert medical witness in the area of nonaccidental injury.